9. Alternate mechanisms of carbon fixation

Question 1

What are stomas

Answer 1

Plant cells responsible for the exchange of CO2 and O2 and the release of water

Question 2

How will stomas react if tempture increases in an unchanged plant

Answer 2

If temp increases, to prevent water loss, plants will close stomata to preserve water

Question 3

What happens to the oxygen and carbon levels of an unchanged plant once the stoma is closed

Answer 3

• Once closing stomata, CO2 can’t go in but photons are still going in producing O2
• Increase O2 level in leaves when stomata closed
• When O2 increased, rubisco doesn’t work well (no sugars or glucose produced)
• Plant will die bc no energy from sugar even though lots of light

Question 4

Where does the calvin cycle occur in unchanged plants

Answer 4

Everywhere in the plant cell

Question 5

What is the name for unchanged plants

Answer 5

C3 Plants

Question 6

What are the two types of cells in C4 Plants

Answer 6

1. Mesophyll shell at top of leaf
2. Bundle sheath at bottom of leaf

Question 7

Why is it good for C4 plants to have two types of cells

Answer 7

• To keep O2 level really low, created a mechanism to move calvin cycle into bundle sheath
• CO2 in environment moves into mesophyll cells, change to C4 molecule which donates carbon into calvin cycle
• No O2 inside the bundle sheath

Question 8

How does the seperation of the calvin cycle in C4 plants prevent plant death

Answer 8

Oxygen can not enter the sheeth where the carbon cycle takes place. Rubisco will not confused CO2 and O2 and every round of the calvin cycle will be effective so the plant gets proper energy.

Question 9

What tupe of seperation does C4 plants use

Answer 9

Separation by Location

Question 10

What is the simularity between C3 and C4 plants

Answer 10

Calvin cycle works the same but is in a different area

Question 11

Where are CAM plants found

Answer 11

Desert Area

Question 12

When does the Stoma open in CAM plants, and where does the CO2 go

Answer 12

• Open stomata at night to allow CO2 in
• Once CO2 in, instead of going through Calvin cycle, CO2 changes to organic acid

Question 13

When does the stoma close in CAM plants and why

Answer 13

• During day, stomata close and use light reactions to use CO2 as a source of making glucose
• During day, organic acid releases CO2, allowing CO2 into calvin cycle

Question 14

Use an analogy to explain how the CAM plants work

Answer 14

• Like putting food in a fridge to eat later

Question 15

Is there a division of location in CAM plants

Answer 15

No

Question 16

What type of seperation do CAM plants use

Answer 16

Separation using time

Question 17

Explain Mesophyll cells

Answer 17

• O2, light reactions
• Loosely arranged around the bundle sheath cells
• Pre calvin cycle reaction occurs in these cells
• CO2 is fixed into a four carbon molecule (malate)
• Four carbon molecules shuttled to bundle-sheath cells

Question 18

Explain bundle-sheath cells

Answer 18

• No O2, dark reactions
• Tightly packed around the veins in the leaf
• Only matale can go in bundle sheath (made for C4 cycle)
• The calvin cycle can only occur in these cells
  
  • • 100% per cycle for greeting G3P
• • Rubisco has high efficiency

Question 19

What does CAM plants stand for

Answer 19

• CAM stands for crassulacean acid metabolism
• Named after the plant family it was first discovered which is succulents

Question 20

What happens in CAM plants during the night

Answer 20

• Stomata open
• CO2 enters leaves and is fixed into organic molecules (malate/malic acid)
• Malate stored in mesophyll cells in vacuoles

Question 21

What happens in CAM plants during the day

Answer 21

• Stoma close
• • Prevent water loss
• Light dependent reactions supply ATP and NADPH for Calvin cycle
• CO2 released from malate which is incorporated into carbohydrate production calvin cycle
• Carbohydrate production during day
• Oxaloacetate available in cells

Question 22

What are the 4 factors that affect photosynthesis

Answer 22

1. Llight
2. Carbon dioxide
3. Tempeture
4. Oxygen concentration

Question 23

How does light affect photosynthesis

Answer 23

• Rate of photosynthesis increases as light intensity increase until all pigments been used - saturation point
• • Light and CO2 are limiting factors

Question 24

How does carbon dioxide affect photosynthesis

Answer 24

• Rate of photosynthesis will increase until the plants overwhelmed by high levels of CO2
• • As light increases, CO2 uptake increases
• • More light you have, more CO2 you need

Question 25

How does tempeture affcet photosynthesis

Answer 25

• Many temperature-dependent enzymes work in this process and therefore demand strict temperature limits to operate at peak efficiency
• • Temp to high OR too low, enzymes responsible for everything will denature

Question 26

How does oxygen concntration affect photosynthesis

Answer 26

• Increase CO2 in plants, O2 is going to complete for rubisco